Chris:

I am glad that you have asked for some clarifications.

The whole point is that we are considering GK-to-GK communications in multiple GK environment. Let there be any number of GKs to participate for GK-to-GK communications depending on specific configurations. It can be as simple as single GK (single zone) or multiple GKs consisting of multiple zones and multiple (administrative)-domains.

Before going to details, I guess that most of the questions that you have asked have been clarified by me on September 1, 1998, in response to Douglas Clowes' questions.

AT&T's contribution is considering the RAS signaling messages only (NOT call setup, media negotiation, or data packets). In response to Mr. Clowes' questions (please see the details in the email sent on Sept 1), it has been explained that, in H.323, a GK's knowledge is limited to zone-level only (no "notion" of network-level path as in the case of IP, ATM, FR, or other networks). The proposal does not mandate what path will be followed by the call setup, media negotiation, or data packets associated with the call.

Yes, AT&T's contribution, like other proposals, also separates between the RAS signaling stage and the call signaling stage. So, the call signaling is free to take any path as appropriate.

In addition to AT&T's contribution, Nokia's APC 1382 (S. Sengodan, Nokia, "On the Use of Multicast Scope for Gatekeeper Discovery," APC 1382, Q.11-14/16 Rapporteur Meeting, Cannes, France, June 8-11, 1998) will also explain why additional fields are needed in signaling messages. The extra fields are primarily needed to facilitate routing of the messages between the GKs in multiple GK environment.

I like to point out that a service provider, in general, can create a variety of back-end services through intercepting signaling messages from the appropriate entities (e.g., GKs) situated in the optimal locations as needed if the signaling messages are allowed to pass through those entities.

I hope that the above explanations will clarify the things.

Regards, Radhika

---

From: Chris Purvis WVdevmt-WS[SMTP:cpurvis@MADGE.COM] Reply To: Mailing list for parties associated with ITU-T Study Group 16 Sent: Monday, September 07, 1998 12:29 PM To: ITU-SG16@MAILBAG.INTEL.COM Subject: Re: Annex G

Radhika,

In my view there is a fundamental difference between the scheme that you are proposing and the other contributions on inter-administrative-domain communication:

Your proposal continues to expect all RAS, call setup, media negotiation and, (for all I know - it's not clear to me in your proposal), data packets associated with a call to follow a path through intermediate entities that are on the path that address resolution messages happened to take.

All the other proposals I have seen preserve a separation between the resolution phase (where messages may indeed need to be sent to a number of different places), and the call signalling stage which follows a more direct route between endpoints.

Your proposal requires the addition of extra fields to almost all RAS messages, and will generate a significant amount of extra call signalling traffic on the global network.

I still fail to understand what the technical (or business) advantages of this extra propogation of messages are. My impression was that the vast majority of the people on last Friday's conference call share my scepticism.

Regards, Chris

-- Dr Chris Purvis - Senior Development Engineer, WAVE CC Software Madge Networks Ltd, Wexham Springs, Framewood Road, Wexham, Berks. Phone:+44 1753 661359 email: cpurvis@madge.com